Small airway diseases (e.g., small airway inflammatory disease, heaves, and chronic obstructive pulmonary disease) are prevalent causes of exercise intolerance, cough, and asthma-like attacks in horses. These clinical symptoms may be precipitated by progressive allergic reactions to dust found in hay and in the environment, but the cause is not always identified. Traditional management includes minimizing the horse's exposure to dust and conventional hay, bronchodilator treatment for immediate relief, steroid treatment to reduce inflammation and bring about remission, and long-term preventative control with inhaled anti-inflammatory agents.